In the United States and throughout the world, anchor bolts are the primary means of securing building structures to concrete foundations. Indeed, most building codes have detailed requirements for such anchor bolts and their placement in concrete constructions. For example, according to some building codes, these anchor bolts must be made of half-inch, L-or J-shaped steel rods, and embedded into the concrete at least six inches deep. In many cases, the structure placed atop the concrete foundation is anchored by securing a sole plate to the anchor bolts. Sole plates are typically 2×4's or 2×6's with holes drilled for placement of the anchor bolts substantially down the center line of the sole plates. The anchor bolts protrude above the concrete far enough to pass through the holes in the sole plate and allow the use of a washer and nut to secure the sole plate to the foundation. Anchor bolts are also used in other contexts. In other applications, builders place anchor bolts, having the same placement and alignment requirements, to affix the base plate of a column or post to a concrete foundation or pad. That is, rather than securing a sole plate near the edge of the foundation, a plurality of anchor bolts, often in a geometric pattern, are used to secure the base plate of a column to a concrete pad.
Ideally, the anchor bolts extend vertically from the foundation, and are placed at the appropriate distance from the edge of the foundation such that they pass through holes in the center line of the sole plate. If the anchor bolts are not vertical or are not aligned properly, they create alignment problems, forcing the holes in the sole plate to be off of the center line. This circumstance may cause the sole plate and the connection to the foundation to be weakened, detrimentally affecting the integrity of the structure. In addition, if an anchor bolt protrudes too far above the sole plate, the anchor bolt is probably not embedded deeply enough in the concrete, which may also compromise the ability of nut to secure the sole plate to the foundation due to thread run out on the bolt shaft. Furthermore, if the anchor bolt does not protrude far enough, the builder will have to chisel or auger a large portion of the sole plate out to create a large cupped-out area with potentially multiple drill holes to correctly locate the low bolt to attach the washer and nut.
To erect a concrete foundation, most often, forms are set; and wet concrete is placed in the forms. The concrete is then “skreeded” to the appropriate grade or elevation. Sometime after the concrete is skreeded and before it cures, anchor bolts are inserted into the still pliable concrete. If the concrete is too wet, the anchor bolts have a tendency to sink or to tilt away from vertical. If the concrete is too hard, placing the anchor bolts tends to create dimples or funnel-shaped depressions (or air pockets) around the anchor bolts. These depressions and resultant stress frequently result in cracks, and a poor bond between the concrete and anchor bold. In addition, placement of anchor bolts in this manner often results in the anchor bolts being either too close or too far from the edge of the foundation, creating alignment problems for attachment of the sole plate. Another problem relating to placement of anchor bolts in this manner is possible damage to the threads of the anchor bolt after placement in the concrete, or the possibility of concrete becoming embedded in the threads.
The circumstances discussed above are not just theoretical possibilities or abstract problems. The applicants inspected 1,450 anchor bolts prior to attachment of sole plates on over thirty different building sites. These anchor bolts had been placed by a number of different contractors. Of the anchor bolts inspected, 55% had dimples (depressions around the anchor bolts between ⅛″ and ⅜″ deep), and 25% had air pockets (depressions around the anchor bolts between ⅜″ and 5″ deep). Of the anchor bolts which had dimples or air pockets, 70% showed at least minor cracking around the anchor bolts and 25% had severe cracking, including all of the anchor bolts which showed air pockets. According to the American Concrete Institute moderate to severe cracks around anchor bolts should be repaired by addition of gravity fed epoxy and drilling holes for remedial anchor bolts.
Laboratory tests were performed on a number of anchor bolts placed in concrete. A variety of strength tests were performed on anchor bolts which showed no dimples or air pockets and upon anchor bolts which showed dimples, air pockets of the less severe variety, and moderate cracking. The tests were performed under International Building Code standards and included the following: 1) concrete breakout strength of anchor bolts in tension [IBC 1913.4.2 & 1913.5.2], 2) pullout strength of anchor bolts in tension [IBC 1913.4.2 & 1913.5.3], 3) concrete side-face blowout strength of anchor bolts in tension [IBC 1913.4.2 & 1913.5.4], and 4) concrete pry-out strength of anchor bolts in shear [IBC 1913.4.2 & 1913.6.3]. The test results showed that anchor bolts with dimples, air pockets of the less severe variety, and moderate cracking were 38% to 50% weaker than anchor bolts without such conditions.
Several attempts have been made to solve at least some of the above described problems associated with the placement of anchor bolts in concrete. U.S. Pat. No. 4,932,818 issued to Garwood, for example, discloses a positioning mechanism, including a threaded plastic sleeve and an opposing flange member that holds an anchor bolt in the hole of a forming template. After concrete is poured, the forming template, including the anchor bolts secured by the positioning system, is placed on top of the curing concrete. U.S. Pat. No. 6,347,916 issued to Ramirez discloses a plastic cap which fits over the treaded end of an anchor bolt. The cap has a disk-shaped base which “floats” on top of the concrete, helping to ensure that the anchor bolt projects the appropriate distance above the concrete and remains vertical. After the concrete is cured, the top portion of the cap is removed, leaving the disk-shaped base in the foundation. Even if an anchor bolt is correctly placed in the concrete, the very act of placement may cause air pockets or dimples around the anchor bolt. As discussed above, such air pockets or dimples weaken the bond between the anchor bolt and the concrete (as set out above) and should be avoided.
Anchor bolts, after placement in a concrete foundation, also raise safety issues. Indeed, there is growing concern within the building industry, and among building construction safety regulators, relating to the possibility of impalement or other injuries caused by protruding steel, such as anchor bolts. For example, the Occupational Safety and Health Administration (OSHA) has promulgated regulations relating to protruding steel at construction sites. Although OSHA regulations do not specifically identify anchor bolts as a potential hazard, there is obviously a possibility that workers, or even trespassers, on the building site could be injured by falling on an anchor bolt which may protrude 2″ to 4″ from the foundation.
In light of the foregoing, a need in the art exists for methods, apparatuses and systems that address the problems discussed above. For example, a need in the art exists for a concrete anchor float that reduces voids and air pockets which may form around anchor bolts, thereby promoting a stronger bond between the anchor bolt and the concrete. A need also exists in the art for methods, apparatuses and systems that help protect against injuries caused by falling on anchor bolts. Embodiments of the present invention substantially fulfill these needs.